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3 years ago

Which statement compares the two numbers correctly?

Mathematics

1 answer:

Vsevolod [243]3 years ago

6 0

Answer:

Step-by-step explanation:

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A rumor spreads through a small town. Let y ( t ) be the fraction of the population that has heard the rumor at time t and assum

Ivan

Answer:

Differential equation

$\frac{dy}{dt} =ky(1-y)$

Solution

$y=\frac{1}{1+4e^{-0.327t}}$

Value of constant k=0.327 days^(-1)

The rumor reaches 80% at 8.48 days.

Step-by-step explanation:

We know

y(t): proportion of people that heard the rumor

y'(t)=ky(1-y), rate of spread of the rumor

Differential equation

$\frac{dy}{dt} =ky(1-y)$

Solving the differential equation

$\frac{dy}{y(1-y)}=k\cdot dt \\\\\int \frac{dx}{y(1-y)} =k \int dt \\\\-ln(1-\frac{1}{y} )+C_0=kt\\\\1-\frac{1}{y} =Ce^{-kt}\\\\\frac{1}{y} =1-Ce^{-kt}\\\\y=\frac{1}{1-Ce^{-kt}}$

Initial conditions:

$y(0)=0.2\\y(3)=0.4\\\\y(0)=0.2=\frac{1}{1-Ce^0}\\\\1-C=1/0.2\\\\C=1-1/0.2= -4\\\\\\y(3)=0.4=\frac{1}{1+4e^{-3k}} \\\\1+4e^{-3k}=1/0.4\\\\e^{-3k}=(2.5-1)/4=0.375\\\\k=ln(0.375)/(-3)=0.327\\\\\\y=\frac{1}{1+4e^{-0.327t}}$

Value of constant k=0.327 days^(-1)

At what time the rumor reaches 80%?

$y(t)=0.8=\frac{1}{1+4e^{-0.327t}} \\\\1+4e^{-0.327t}=1/0.8=1.25\\\\e^{-0.327t}=(1.25-1)/4=0.0625\\\\t=ln(0.0625)/(-0.327)=8.48$

The rumor reaches 80% at 8.48 days.

8 0

3 years ago

Use the properties of exponents to rewrite y=e^-0.75t in the form of a(1-r)^t

Ivahew [28]

Answer: y = (1 - 0.527)^t

Step-by-step explanation:

y=e^(-0.75t)

y=(e^-0.75)^t

y= 0.47236655^t

1 - 0.47236655 = 0.52763345

y = (1 - 0.527)^t

5 0

2 years ago

What is the answer to -5(-3w-8)=21 for w

Sauron [17]

Answer:

w = -1.266

Step-by-step explanation:

distribute the 5 by everything in the parenthesis and then bring everyhting down then you should have a regular equation to work w

8 0

3 years ago

It is 4 : 12 p.M. 4:12 p.M.4, colon, 12, start text, space, p, point, m, point, end text Emma's mom will be home from work in 70

Vaselesa [24]

Answer:

40 Minutes.

Step-by-step explanation:

The current time = 4:12 p.M.

Emma's mom will be home from work in 70 minutes.

70 minutes = 1 hour 10 Minutes= 1: 10 Hours

$\left\begin{array}{ccccc}&4&:&12 &p.m.\\+&1&:&10&\\--&--&--&--&--\\&5&:&22&p.m\end{array}\right$

Therefore, Emma's Mom will get home by 5: 22 p.m.

Emma has gymnastics lessons at 6 : 00 p.M.

To determine how much time Emma will have between the time that her mom gets home from work and the beginning of gymnastics lessons, we simply subtract 5:22 from 6.

$\left\begin{array}{ccccc}&6&:&00 &p.m.\\-&5&:&22&\\--&--&--&--&--\\&00&:&40&\end{array}\right$

Emma will have 40 Minutes.

5 0

3 years ago

What is 127 to the nearest 10

finlep [7]

Answer:The answer is 130

Step-by-step explanation:

3 0

3 years ago